The major objective of this application has been to explore the hormonal and nutritional regulation of intermediary metabolism, and to clarify hormone-vitamin relationships. Among the major studies in progress are the following: (1) effects of maternal riboflavin deficiency in rats upon the rates of flavin synthesis in newborn liver and brain. These data provide evidence that maternal riboflavin deficiency greatly enhances the rates of incorporation of riboflavin into flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), and acid non-extractable flavins in liver, cerebrum and cerebellum of newborn rats. (2) Regulation of L-triiodothyronine amino-transferase activity by thyroid hormones. These data suggest that triiodothyronine (T3) and thyroxine (T4) may regulate the rates of their own inactivation at least in part through transamination in liver. (3) Thyroid hormone control of formation of covalently-bound flavins. These data indicate that thyroid hormone control of flavin synthesis in liver is not limited to free falvins, but also extends to flavins linked covalently to tissue proteins. (4) Studies of taste and smell sensations in animals and patients with reduced thyroid function. These studies show that severe, reversible defects in taste and smell sensations in man, and in taste sensations in rats are produced by hypothyroidism.